The roots of the American Federation of Labor-Congress of Industrial Organizations (AFL-CIO), today a federation of national unions, date to 1881 when the Federation of Organized Trade and Labor Unions was formed in Pittsburgh, Pennsylvania, by trade union leaders representing some 50,000 members in the United States and Canada. Reorganizing in 1886, the association of unions changed its name to the American Federation of Labor (AFL) and elected Samuel Gompers (1850–1924) president.

Unlike the open-membership policy of the Knights of Labor (from whom the AFL gained numerous members in 1886), the AFL determined to organize by craft: At the outset, its member unions included a total of 140,000 skilled laborers. Gompers, who immigrated from England in 1863 and became the first registered member of the Cigar-Makers’ International Union in 1864, had been active in labor for more than two decades. Once chosen as president of the AFL, Gompers remained in that office, with the exception of only one year, until his death in 1924. During the nearly 40-year period, he shaped the labor federation and helped it make strides by determining a general policy that allowed member unions autonomy. Unlike the Knights of Labor, which pursued long-term goals such as Knights leader Terence Powderly’s abstract objective of making “every man his own master—every man his own employer,” the AFL focused its efforts on specific, short-term goals such as higher wages, shorter hours, and the right to bargain collectively (when an employer agrees to negotiate with worker/union representatives).

In the 1890s the AFL was weakened by labor violence, which evoked public fears. A July 1892 strike at the Carnegie Steel plant in Homestead, Pennsylvania, turned into a riot between angry steelworkers and Pinkerton guards. The militia was called in to monitor the strike, which five months later ended in failure for the AFL-affiliated steel-workers. Nevertheless, under Gompers’s leadership, membership of the AFL grew to more than 1 million by 1901 and to 2.5 million by 1917, when it included 111 national unions and 27,000 local unions. The federation collected dues from its members, creating a fund to aid striking workers. The organization avoided party politics, instead seeking out and supporting advocates regardless of political affiliation. The AFL worked to support the establishment of the U.S. Department of Labor (1913), which administers and enforces statutes promoting the welfare and advancement of the American workforce, and the passage of the Clayton Anti-Trust Act (1914), which strengthened the Sherman Anti-Trust Act of 1890, eventually delivering a blow to monopolies.

The CIO was founded in 1938. In the early 1930s several AFL unions banded together as the Committee for Industrial Organization and successfully conducted campaigns to sign up new members in mass-production facilities such as the automobile, steel, and rubber industries. Since these initiatives (which resulted in millions of new members) were against the AFL policy of signing up only skilled laborers by craft (the CIO had reached out to all industrial workers, regardless of skill level or craft), a schism resulted within the AFL. The unions that had participated in the CIO membership drive were expelled from the AFL; the CIO established itself as a federation in 1938, officially changing its name to the Congress of Industrial Organizations.

In 1955, amidst a climate of increasing anti-unionism, the AFL and CIO rejoined to form one strong voice. Today the organization has craft and industrial affiliates at the international, national, state, and local levels, with membership totaling in the millions.